Image forming apparatus and method of warning life of charging roller in image forming apparatus

Abstract

An image forming apparatus includes a charging roller, a temperature sensor, a humidity sensor, a sampling part, a life consumption degree calculating part and a warning processing part. The sampling part executes temperature/humidity inputting process inputting temperature of the temperature sensor and humidity of the humidity sensor. The life consumption degree calculating part calculates a life consumption degree of the charging roller from a last time to a present time in the temperature/humidity inputting process by applying respective representative values of last and present inputted temperature and humidity into a model formula. The warning processing part outputs a warning when an addition value of the life consumption degrees exceeds a predetermined threshold value. The life consumption degree calculating part uses the model formula deriving larger life consumption degree in a case where the representative value of the temperature and the representative value of the humidity are respectively larger.

What is claimed is: 
     
       1. An image forming apparatus comprising:
 a charging roller electrically charging an image carrier; 
 a temperature sensor detecting temperature in an environment of the charging roller; 
 a humidity sensor detecting humidity in the environment of the charging roller; and 
 a processor, 
 wherein the processor is configured so as to execute: 
 a sampling part executing temperature and humidity inputting process inputting detected temperature of the temperature sensor and detected humidity of the humidity sensor at a predetermined timing; 
 a life consumption degree calculating part calculating a life consumption degree of the charging roller per a period from a last executing point to a present executing point in the temperature and humidity inputting process by applying respective representative values of last and present inputted detected temperature and detected humidity into a predetermined model formula every time the temperature and humidity inputting process is executed; and 
 a warning processing part outputting a warning in a case where an addition value of the life consumption degrees exceeds a predetermined threshold value, 
 wherein the life consumption degree calculating part uses, as the model formula, an expression deriving larger life consumption degree in a case where the representative value of the detected temperature and the representative value of the detected humidity are respectively larger, as compared with a case where they are smaller. 
 
     
     
       2. The image forming apparatus according to  claim 1 , wherein
 the life consumption degree calculating part uses, as the model formula, an expression deriving a ratio of a time to a derived value of an exponential function, in which the time is from the last executing point to the present executing point in the temperature and humidity inputting process, and the exponential function has an exponent of a derived value of a primary linear polynomial expression having two variables of the reciprocal of the representative value of the detected temperature and the representative value of the detected humidity. 
 
     
     
       3. The image forming apparatus according to  claim 1 , wherein
 the life consumption degree calculating part uses an average value as the respective representative values of the detected temperature and the detected humidity. 
 
     
     
       4. The image forming apparatus according to  claim 1 , wherein
 the life consumption degree calculating part calculates the life consumption degree by calculating a reduction rate of a substance amount of the charging roller per a period from the last executing point to the present executing point in the temperature and humidity inputting process. 
 
     
     
       5. The image forming apparatus according to  claim 4 , wherein
 the life consumption degree calculating part calculates the reduction rate of the substance amount of the charging roller on the basis of proportion of a reducing speed of the substance amount due to a chemical reaction to n-th power of the substance amount before the chemical reaction. 
 
     
     
       6. The image forming apparatus according to  claim 1 , wherein
 the life consumption degree calculating part calculates the life consumption degree y k  per period Δt k , by using formulas: x=(α/T k )+(β/RH k )+γ; and y k =Δt k /exp(x), as the model formula using: the representative value T k  of the detected temperature; the representative RH k  value of the detected humidity; the derived value x of the exponential function; and constants α, β, γ. 
 
     
     
       7. A method of warning a life of a charging roller in an image forming apparatus including a charging roller electrically charging an image carrier, comprising:
 a sampling step executed by a processor included in the image forming apparatus to execute temperature and humidity inputting process inputting detected temperature and detected humidity in an environment of the charging roller at a predetermined timing; 
 a life consumption degree calculating step executed by the processor to calculate a life consumption degree of the charging roller per a period from a last executing point to a present executing point in the temperature and humidity inputting process by applying respective representative values of last and present inputted detected temperature and detected humidity into a predetermined model formula every time the temperature and humidity inputting process is executed; and 
 a warning processing step executed by the processor to output a warning in a case where an addition value of the life consumption degrees exceeds a predetermined threshold value, 
 wherein the life consumption degree calculating step uses, as the model formula, an expression deriving larger life consumption degree in a case where the representative value of the detected temperature and the representative value of the detected humidity are respectively larger, as compared with a case where they are smaller. 
 
     
     
       8. The method of warning the life of the charging roller according to  claim 7 , wherein
 the life consumption degree calculating step uses, as the model formula, an expression deriving a ratio of a time to a derived value of an exponential function, in which the time is from the last executing point to the present executing point in the temperature and humidity inputting process, and the exponential function has an exponent of a derived value of a primary linear polynomial expression having two variables of the reciprocal of the representative value of the detected temperature and the representative value of the detected humidity. 
 
     
     
       9. The method of warning the life of the charging roller according to  claim 8 , wherein
 the life consumption degree calculating step calculates the life consumption degree y k  per period Δt k , by using formulas: x=(α/T k )+(β/RH k )+γ; and y k =Δt k /exp(x), as the model formula using: the representative value T k  of the detected temperature; the representative RH k  value of the detected humidity; the derived value x of the exponential function; and constants α, β, γ.